The use of lasers in manufacturing/materials processing (e.g. drilling, welding, etc.) historically required locating the laser close to the workpiece being subjected to processing. Various optical components, such as mirrors, beam splitters and lenses, were used to direct and focus the laser beam at each desired point on the workpiece where a processing operation was required. This implicitly required precise alignment of the optical components and workpiece to achieve a successful process operation.
More recently, the transmission of laser beams through optical fibers, at power levels suitable for performing materials processing, has been successfully demonstrated. Various techniques for the efficient injection of a power laser beam into an optical fiber for transmission therethrough are disclosed, for example, in commonly assigned U.S. Pat. Nos. 4,564,736; 4,676,5S6; and 4,681,396 respectively entitled "Industrial Hand Held Laser Tool and Laser System", "Apparatus and Method for Performing Laser Material Processing Through a Fiber Optic", and "High Power Laser Energy Delivery System", which are incorporated in their entirety herein by reference. Such beam transmission through optical fibers has obviated both the need for positioning the laser close to the workpiece and the optical components otherwise required for directing the laser beam to the desired process points on the workpiece. It is instead required to terminate an output end of each optical fiber with an output coupling device that collimates and focuses the beam emitted by the fiber. Laser materials processing is thus enhanced by the great flexibility afforded by the optical fibers in transmitting the laser beam to any desired process points on the workpiece. The number of fibers, and their respective output ends, that need to be simultaneously positioned proximate the process points on the workpiece varies with the particular process. The ability to position optical fibers close together to accommodate the processing requirements of a particular workpiece is limited by the space requirements of the respective fiber output coupling devices. In some applications, such as the manufacture of microelectronic components, it is desirable to achieve very close spacing of the fibers to accommodate closely spaced process points on the workpiece, e.g., soldering a plurality of adjacent electrical terminal pads.
Also available to enhance laser materials processing are systems for the time sharing of a materials processing laser beam among a plurality of optical fibers. Manufacturers of such beam time sharing systems include Robolase Systems, Inc. of Costa Mesa, Calif. and Lumonics Corporation of Livonia, Mich. By the use of such beam time sharing systems, the beam generated by one laser can be shared among multiple optical fibers the respective output ends of which are positioned proximate the process points on one or more workpieces. As a result, the number of optical fibers that can be simultaneously positioned about a workpiece in a manufacturing/materials processing system is limited by the number of lasers, the number of time sharing systems and the number of fibers that can be simultaneously accommodated by each time sharing system. One disadvantage inherent in such a configuration of equipment, in the case of a repetitive manufacturing process, is that the failure of a single fiber adversely affects the entire process, so that the overall process reliability is in direct proportion to the number of fibers in use. It would therefore be desirable to accommodate the same number of process points on the workpiece with a reduced number of optical fibers. In a conventional laser-materials processing system employing fiber delivery of laser beams, the number of fibers could be reduced by the use of conventional beam splitting hardware, e.g. prisms, mirrors, etc., to split the fiber delivered beam (after collimation). Such additional optical hardware is, however, cumbersome and requires considerable mounting hardware to constantly maintain a precise alignment.
It would further be desirable to serve additional process points without providing additional lasers or time sharing systems. This is especially desirable in consideration of the substantial capital investments required for lasers and time sharing systems. Another disadvantage inherent in the time sharing equipment is an apparent inability to differentiate between the respective amounts of laser energy transmitted through the multiple fibers sharing the same laser. Such laser power differentiation would be desirable where different process points on the same workpiece require different amounts of laser energy to perform the desired process.